Energy Saving Opportunities in an Air Conditioner by Lowering the Inlet Air Temperature to the Condenser

Abstract

Energy is a very significant factor in driving durable economic growth and development of any country. Decrease of energy consumption through efficient energy use or by reducing the consumption of energy sources is a goal in all engineering fields. Air conditioning systems are nowadays commonly used in buildings due to the improvement of both quality of life and comfort levels in the society. According to literature review, refrigeration and air conditioning system, based on mechanical vapor compression system consumes about 15% of world’s total electricity consumption. Since huge numbers of air conditioners are in use, therefore any considerable improvement in the performance of the cycle will have huge effect on the power saving. Split air conditioner works on VCR (vapor compression refrigeration) cycle with an air cooled condenser in an ODU (Outdoor Unit). Temperature of air-cooled condenser is directly depended on the ambient air temperature, therefore, in the region like Ahmedabad where in summer ambient air temperature remains very high, the condenser temperature and pressure increase considerably which consequently rises the power consumption of the air conditioner due to this increased pressure ratio. Increasing condenser temperature also decreases the cooling capacity of the VCR cycle due to the less liquid refrigerant mass entry in to the evaporator. These two effects decrease performance of air conditioner considerably at high ambient temperature in summer. In order to improve the performance of air conditioner in these situations, one of the way is to decrease inlet air temperature to the condenser. A well known, method for decreasing inlet air temperature is to use evaporative cooling pad before the condenser coil. The objective of present project work is to study the performance of air conditioning system using evaporative cooling pads and to determine optimum thickness and material of cooling pad. For this purpose, experiments are conducted on 0.8 Ton capacity split air conditioning system with refrigerant R-22, where the condensing unit is modified by coupling different cooling pad with different thickness. The effect of different cooling pad on the overall performance of air conditioning system is experimentally determined by measuring the flow rate, temperature and relative humidity of the condenser air and the energy consumption of the system including water circulation pump. From the conducted experiments it is concluded that cellulose pad gives the best cooling efficiency among the selected material. For cellulose pad of 100 mm thickness at 32% relative humidity, there is an approximate 13.76% increase in actual COP, 9.49 % reduction in power consumption and 5.07 % increase in refrigerating effect.